The Evolution of Green Roofing / Stormwater Management
Ancient: Green roofing has existed for thousands of years and actually has claim to one of the Ancient Seven Wonders of the World, the Hanging Gardens of Babylon. The Ancient Babylonians were said to have had an intricate irrigation system that harvested water from the Tigris and Euphrates Rivers to irrigate the capital of the empire and their magnificent Hanging Gardens.
Medieval: Since the ancient times, green roofing generally referred to structures made from earthen resources like the Incan metropolis of Machu Picchu. The civil engineers of Machu Picchu are highly revered for their rainwater management system which consisted of a vast network of terraces along the mountain side to control water flow. They designed a drainage system into this network that produced enough water pressure to operate numerous fountains within the city. Even with that celebration of excellence, the Inca’s had a surplus water supply for their people.
Modern: At the beginning of the 20th century‚ garden rooftops gained an elitist reputation with the rise of the skyscraper. The garden provided welcome respite for social events during summer months, and they appeared on such buildings as New York City’s Waldorf Astoria Hotel. Mid century, when air-conditioning was invented, the garden-roof was no longer included in the design plans because humans preferred to take refuse indoors. It was not until the 1970’s environmental paradigm shift that green roofing began its resurgence.
Today: The resurgence of stormwater management began in Europe, particularly in Germany, and the industry is now growing rapidly in North America. Due to the density of most European cities, proper stormwater management is vital for the health and aesthetics of urban landscapes, thus they have incorporated stormwater management as common practice. North American cities such as Chicago, Mexico City, Washington D.C., New York, Portland, Toronto and Milwaukee have established either grant or incentive programs to promote green roofs and stormwater management.
Future: Due to the increasing urbanization worldwide combined with steadily rising population, stormwater management will become more prevalent in the future. It will be part of comprehensive development plans, in tandem with on-grade storm water mitigation design, which will harvest 100% of the rain water from buildings. In addition, as our cities evolve, it will be necessary to maximize the use of available space to grow and harvest fresh produce. The future will bring an ever expanding system of vertical and roof top agriculture that will offer healthy solutions to feed a growing population.
The Industry
The primary purpose of green roofs is to mitigate storm water from entering the combined sewage districts of urban centers. During heavy rain events, the combined sewage systems cannot treat the water fast enough, which causes polluted water to be discharged into the waterways, reservoirs & aquifers where our drinking water is drawn. According to a recent publication from Green Roofs for Healthy Cities, this is a large expense for municipalities, which is the prime reason the market for green roof products grew 28.5% in 2010 ( “Greenroof Industry Grows 28.5% in 2010”, Sustainable Business News, March 31, 2011) and has been growing at an average rate of 25% for the past ten years. The most common style of green roof system is known as the monolithic system (where each component is installed in layers). This system dominates 95% of the European market and has gained an increasing popularity in the American market over the past five years.
Stormwater Mitigation Industry
Fresh water is our most precious and increasingly scarce natural resource. Since the inception of the EPA’s 1972 Clean Water Act, our country has become more connected with the preservation and protection of water. They knew then that an increasing population and constantly changing climate had started to make the availability of fresh water a grave concern among governing bodies around the world. It is with the Clean Water Act that the industry has grown exponentially over the past four decades. These laws and increasing environmental concern around meeting fresh water needs is driving the demand for products and systems that harvest stormwater. Biological Mitigation, a form of Low-Impact Development, offers a sustainable solution to manage the excess rainwater from impervious surfaces (Green roofs are an example of Biological Mitigation). This style of stormwater mitigation offers a cost-effective and efficient way to restore the natural landscape while ensuring an abundant supply of water for a growing population.